Effect of estrogen on nitric oxide-induced relaxation of the rabbit urethra.
We evaluated the effect of estrogen on nitric oxide (NO)-mediated urethral relaxation in rabbits. Female New Zealand white rabbits, 4-5 weeks old, were treated with 5 mg/kg estradiol dipropionate (estrogen group) or saline (control group) injected intramuscularly weekly for 2 weeks. Electrical field stimulation (supramaximum voltage, 2 ms pulse duration, 0.3-15 Hz and 3 s train) caused frequency-dependent relaxation of urethral strips in both groups, which was inhibited by Nomega-nitro-L-arginine (L.-NNA). This inhibition was overcome by addition of L-arginine. The relaxation induced by nitrergic nerve stimulation was significantly lower in the estrogen group than in the control group. There was no significant difference in sodium nitroprusside-induced urethral relaxation between the two groups. The production of NO in urethral strips during nitrergic nerve stimulation was evaluated by measuring nitrite/nitrate (NO2-/NO3-) levels in both groups, using microdialysis. The NO2-/NO3- production during electrical field stimulation in the estrogen group was significantly less than that in the control group. The NADPH diaphorase-positive reaction in the control group was greater than that in the estrogen group. The results suggest that estrogen treatment may reduce NO synthase activity, and inhibit the relaxation induced by nitrergic nerve stimulation in rabbit urethral smooth muscle.
Takahashi
W
W
Department of Urology, Kumamoto University School of Medicine, Honjo, Japan.
Yoshida
M
M
Wada
Y
Y
Goto
S
S
Inadome
A
A
Yono
M
M
Ueda
S
S
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D001835:Body Weight / Q000187:drug effects; D002316:Cardiotonic Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D005260:Female; D009126:Muscle Relaxation / Q000187:drug effects*; D009252:NADPH Dehydrogenase / Q000378:metabolism*; D009569:Nitric Oxide / Q000502:physiology*; D009599:Nitroprusside / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011817:Rabbits; D014521:Urethra / Q000187:drug effects* / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology
D000319:Adrenergic beta-Antagonists; D000889:Anti-Arrhythmia Agents; D002316:Cardiotonic Agents; D014665:Vasodilator Agents; D009599:Nitroprusside; D010656:Phenylephrine; D009569:Nitric Oxide; D004958:Estradiol; D001285:Atropine; D011433:Propranolol; D009252:NADPH Dehydrogenase; C023482:estradiol dipropionate